xv6-65oo2/kernel/console.c

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//
// Console input and output, to the uart.
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// Reads are line at a time.
// Implements special input characters:
// newline -- end of line
// control-h -- backspace
// control-u -- kill line
// control-d -- end of file
// control-p -- print process list
//
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Checkpoint port of xv6 to x86-64. Passed usertests on 2 processors a few times. The x86-64 doesn't just add two levels to page tables to support 64 bit addresses, but is a different processor. For example, calling conventions, system calls, and segmentation are different from 32-bit x86. Segmentation is basically gone, but gs/fs in combination with MSRs can be used to hold a per-core pointer. In general, x86-64 is more straightforward than 32-bit x86. The port uses code from sv6 and the xv6 "rsc-amd64" branch. A summary of the changes is as follows: - Booting: switch to grub instead of xv6's bootloader (pass -kernel to qemu), because xv6's boot loader doesn't understand 64bit ELF files. And, we don't care anymore about booting. - Makefile: use -m64 instead of -m32 flag for gcc, delete boot loader, xv6.img, bochs, and memfs. For now dont' use -O2, since usertests with -O2 is bigger than MAXFILE! - Update gdb.tmpl to be for i386 or x86-64 - Console/printf: use stdarg.h and treat 64-bit addresses different from ints (32-bit) - Update elfhdr to be 64 bit - entry.S/entryother.S: add code to switch to 64-bit mode: build a simple page table in 32-bit mode before switching to 64-bit mode, share code for entering boot processor and APs, and tweak boot gdt. The boot gdt is the gdt that the kernel proper also uses. (In 64-bit mode, the gdt/segmentation and task state mostly disappear.) - exec.c: fix passing argv (64-bit now instead of 32-bit). - initcode.c: use syscall instead of int. - kernel.ld: load kernel very high, in top terabyte. 64 bits is a lot of address space! - proc.c: initial return is through new syscall path instead of trapret. - proc.h: update struct cpu to have some scratch space since syscall saves less state than int, update struct context to reflect x86-64 calling conventions. - swtch: simplify for x86-64 calling conventions. - syscall: add fetcharg to handle x86-64 calling convetions (6 arguments are passed through registers), and fetchaddr to read a 64-bit value from user space. - sysfile: update to handle pointers from user space (e.g., sys_exec), which are 64 bits. - trap.c: no special trap vector for sys calls, because x86-64 has a different plan for system calls. - trapasm: one plan for syscalls and one plan for traps (interrupt and exceptions). On x86-64, the kernel is responsible for switching user/kernel stacks. To do, xv6 keeps some scratch space in the cpu structure, and uses MSR GS_KERN_BASE to point to the core's cpu structure (using swapgs). - types.h: add uint64, and change pde_t to uint64 - usertests: exit() when fork fails, which helped in tracking down one of the bugs in the switch from 32-bit to 64-bit - vectors: update to make them 64 bits - vm.c: use bootgdt in kernel too, program MSRs for syscalls and core-local state (for swapgs), walk 4 levels in walkpgdir, add DEVSPACETOP, use task segment to set kernel stack for interrupts (but simpler than in 32-bit mode), add an extra argument to freevm (size of user part of address space) to avoid checking all entries till KERNBASE (there are MANY TB before the top 1TB). - x86: update trapframe to have 64-bit entries, which is what the processor pushes on syscalls and traps. simplify lgdt and lidt, using struct desctr, which needs the gcc directives packed and aligned. TODO: - use int32 instead of int? - simplify curproc(). xv6 has per-cpu state again, but this time it must have it. - avoid repetition in walkpgdir - fix validateint() in usertests.c - fix bugs (e.g., observed one a case of entering kernel with invalid gs or proc
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#include <stdarg.h>
#include "types.h"
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#include "param.h"
#include "spinlock.h"
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#include "sleeplock.h"
#include "fs.h"
#include "file.h"
#include "memlayout.h"
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#include "riscv.h"
#include "defs.h"
#include "proc.h"
#define BACKSPACE 0x100
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#define C(x) ((x)-'@') // Control-x
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//
// send one character to the uart.
// called by printf, and to echo input characters,
// but not from write().
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//
void
consputc(int c)
{
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if(c == BACKSPACE){
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// if the user typed backspace, overwrite with a space.
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uartputc_sync('\b'); uartputc_sync(' '); uartputc_sync('\b');
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} else {
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uartputc_sync(c);
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}
}
struct {
struct spinlock lock;
// input
#define INPUT_BUF 128
char buf[INPUT_BUF];
uint r; // Read index
uint w; // Write index
uint e; // Edit index
} cons;
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//
// user write()s to the console go here.
//
int
consolewrite(int user_src, uint64 src, int n)
{
int i;
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acquire(&cons.lock);
for(i = 0; i < n; i++){
char c;
if(either_copyin(&c, user_src, src+i, 1) == -1)
break;
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uartputc(c);
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}
release(&cons.lock);
return i;
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}
//
// user read()s from the console go here.
// copy (up to) a whole input line to dst.
// user_dist indicates whether dst is a user
// or kernel address.
//
int
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consoleread(int user_dst, uint64 dst, int n)
{
uint target;
int c;
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char cbuf;
target = n;
acquire(&cons.lock);
while(n > 0){
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// wait until interrupt handler has put some
// input into cons.buffer.
while(cons.r == cons.w){
if(myproc()->killed){
release(&cons.lock);
return -1;
}
sleep(&cons.r, &cons.lock);
}
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c = cons.buf[cons.r++ % INPUT_BUF];
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if(c == C('D')){ // end-of-file
if(n < target){
// Save ^D for next time, to make sure
// caller gets a 0-byte result.
cons.r--;
}
break;
}
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// copy the input byte to the user-space buffer.
cbuf = c;
if(either_copyout(user_dst, dst, &cbuf, 1) == -1)
break;
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dst++;
--n;
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if(c == '\n'){
// a whole line has arrived, return to
// the user-level read().
break;
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}
}
release(&cons.lock);
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return target - n;
}
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//
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// the console input interrupt handler.
// uartintr() calls this for input character.
// do erase/kill processing, append to cons.buf,
// wake up consoleread() if a whole line has arrived.
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//
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void
consoleintr(int c)
{
acquire(&cons.lock);
switch(c){
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case C('P'): // Print process list.
procdump();
break;
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case C('U'): // Kill line.
while(cons.e != cons.w &&
cons.buf[(cons.e-1) % INPUT_BUF] != '\n'){
cons.e--;
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consputc(BACKSPACE);
}
break;
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case C('H'): // Backspace
case '\x7f':
if(cons.e != cons.w){
cons.e--;
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consputc(BACKSPACE);
}
break;
default:
if(c != 0 && cons.e-cons.r < INPUT_BUF){
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c = (c == '\r') ? '\n' : c;
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// echo back to the user.
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consputc(c);
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// store for consumption by consoleread().
cons.buf[cons.e++ % INPUT_BUF] = c;
if(c == '\n' || c == C('D') || cons.e == cons.r+INPUT_BUF){
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// wake up consoleread() if a whole line (or end-of-file)
// has arrived.
cons.w = cons.e;
wakeup(&cons.r);
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}
}
break;
}
release(&cons.lock);
}
void
consoleinit(void)
{
initlock(&cons.lock, "cons");
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uartinit();
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// connect read and write system calls
// to consoleread and consolewrite.
devsw[CONSOLE].read = consoleread;
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devsw[CONSOLE].write = consolewrite;
}